The present invention relates generally to medical devices and more particularly to balloon catheters.
Various medical conditions may affect patients in a variety of bodily passageways, such as vessels and ducts. One common condition is atherosclerosis, which begins with the accumulation of excess fats and cholesterol in a blood vessel. Atherosclerotic plaque forms within the walls of the vessel and may block or restrict blood flow through the vessel. This narrowed portion of the arterial lumen is commonly referred to as a stricture or stenosis. Generally, the coronary arteries, the aorta, the iliofemoral arteries and the carotid arteries are most commonly affected by stenosis. Several serious consequences may result from the restricted blood flow, such as ischemic events and blood clots that may block the artery.
There are various types of athlerosclerotic plaque that may form within the vessel wall. For example, some plaque may impede flow and exhibit a calcified or fibrous nature, while other plaque may be considered “vulnerable plaque.” While vulnerable plaque may develop within the arterial walls without generally narrowing the arterial lumen substantially, occlusive lesions may include calcified or fibrous plaque comprising, for example, necrotic tissue. The necrotic tissue associated with fibrous plaque may cause the arterial wall to progressively weaken, and a rupture of the intima can occur, thereby causing aneurysm and hemorrhage.
Various procedures are known for treating such occlusions in the arterial vasculature, including balloon angioplasty and stenting. Although balloon catheters are used in many procedures other than angioplasty, coronary angioplasty using a balloon catheter has drawn particular attention from the medical community because of the growing number of people suffering from heart problems associated with stenosis. This has lead to an increased demand for medical procedures to treat such problems. The increased frequency of heart problems in recent years may be due to a number of societal changes, including, but not limited to insufficient exercise, obesity, and unhealthy diets in conjunction with an increase in the average life span as compared to previous generations.
Angioplasty procedures have become a popular alternative for treating coronary stenosis because angioplasty procedures are considerably less invasive than other alternatives. For example, stenosis of the coronary arteries has traditionally been treated with bypass surgery. In general, coronary bypass surgery is a very invasive procedure that is risky and requires a long recovery time for the patient. Typically, bypass surgery involves splitting the chest bone to open the chest cavity and grafting a replacement vessel onto the heart to bypass the blocked, or stenosed, artery.
During a balloon angioplasty procedure, a catheter having a deflated balloon attached thereto is inserted into a patient's vessel. During this stage, the balloon is uninflated and collapsed onto the catheter in order to present a low profile which may be passed through vessel lumens. Once positioned across a constricting lesion, the balloon is inflated by pumping a saline solution or a mixture of saline and contrast solution through the catheter to the balloon. As the balloon inflates, it is forced against the vessel wall and expands radially outward to widen the lumen to partially or fully restore patency to the vessel. This outward expansion of the vessel is typically referred to as dilation.
In the event a stent is mounted on the balloon, the balloon inflation may also serve to expand the stent and implant it within the artery. After satisfactory widening of the stenosis has been achieved, the balloon is deflated so that it once again collapses onto the delivery system. The catheter then is retracted and removed from the patient's vessel with the balloon in the deflated state. The balloon catheter is then retracted from the body. If a stent is mounted on the balloon of the catheter, the stent is left permanently implanted in its expanded state at the desired location in the vessel to provide a support structure that prevents the vessel from collapsing back to its pre-dilated condition. On the other hand, if the balloon catheter is not adapted for delivery of a stent, either a balloon-expandable stent or a self-expandable stent may be implanted in the dilated region in a follow-up or follow-on procedure.
It is not uncommon for stenosed regions to be formed of calcified or fibrous plaque comprising, for example, necrotic tissue. These types of stenosis can be difficult to completely dilate using conventional balloons because they tend to remain intact and resist expansion pressures applied by conventional balloon catheters.